With brand loyalty becoming increasingly important in adding value and differentiating goods in the market place, it is important for brand owners to monitor the authenticity and use of their products. To this end, covert security features are frequently applied to goods to authenticate that they are genuine. Examples of covert security features include markings in ink that is invisible in visible light but fluoresces under UV light, as described in EP 01 196 297 and GB 2 366 645. Similar features are known that employ IR sensitive inks rather than UV sensitive inks, as described in EP 00 988 150.
Security may be improved by providing multiple security features. US 2005/0 092 844 describes an information card having a multitude of security features such as magnetic strips, RF-ID tags, integrated circuits and composite barcodes. Further security may be added by providing a relationship between two security features such that both security features need to be read to provide the security information. Examples of this are described in EP 01 610 263.
As counterfeiters become adept at detecting and copying covert security features, new security features are required.